1. Technical Field
This invention relates to compositions useful for converting hydrogen sulfide or other organic sulfides such as mercaptans from fluid streams, and more particularly, to an amine resin solution made by reacting sterically hindered amines such as selected alkyl diamines, alkyl triamines, amino alcohols and mixtures thereof with aldehydes, aldehyde donors, or the reaction products of lower alkanolamines and lower aldehydes.
2. Prior Art
The use of lower alkanolamines and lower aldehydes in compositions for sweetening gaseous and liquid hydrocarbon streams is well known, having previously been disclosed, for example, in U.S. Pat. Nos. 4,748,011 and 4,978,512.
U.S. Pat. No. 4,748,011 discloses a method for the separation and collection of natural gas through use of a sweetening solution comprising an aldehyde or ketone, methanol, an amine inhibitor (including alkanolamines), sodium or potassium hydroxides, and isopropanol.
U.S. Pat. No. 4,978,512 discloses a method for selectively reducing the levels of hydrogen sulfide and organic sulfides present in gaseous or liquid hydrocarbon streams or mixtures thereof by contacting the streams with a composition comprising the reaction product of a lower alkanolamine with a lower aldehyde.
U.S. Pat. No. 2,390,153 discloses a process for solubilizing a water and organic solvent insoluble nitrogenous condensation product of hexamethylene diamine and formaldehyde by heating the condensation product with three times its weight of 30% aqueous formaldehyde solution, preferably in the presence of butyl alcohol, until the condensation product becomes soluble.
U.S. Pat. No. 3,856,921 discloses the removal of carbon dioxide and carbonyl sulfide from fluids by contacting the fluids with a solution of a basic salt of an alkali or alkaline earth metal and an amine.
U.S. Pat. No. 4,112,050 discloses the removal of carbon dioxide containing gases from normally gaseous mixtures by contacting the mixtures with a solution comprising a basic alkali metal salt or hydroxide and an activator comprising at least one sterically hindered amine.
U.S. Pat. No. 4,112,051 discloses the removal of acidic gases, including hydrogen sulfide, from normally gaseous mixtures by contacting the mixtures with an amine-solvent liquid absorbent comprising an amine having at least about 50 mol percent of a sterically hindered amine and a solvent for the amine mixtures which is also a physical absorbent for the acidic gases.
U.S. Pat. No. 4,112,052 discloses the removal of carbon dioxide containing gases from normally gaseous mixtures by contacting the mixtures with an aqueous amine solution wherein at least one of the amines is a sterically hindered amine.
The processes disclosed in each of U.S. Pat. Nos. 4,112,050, 4,112,051 and 4,112,052 involve the use of a regeneration step in which carbon dioxide is desorbed from the scrubbing solution.
Sartori and Savage have disclosed steric hindrance as the dominant factor giving high thermodynamic capacity and fast absorption rates at high carbon dioxide loadings in aqueous amino alcohols in "Sterically Hindered Amines for CO.sub.2 Removal from Gases" in I & EC FUNDAMENTALS, Vol. 2, No. 22 (1983).
Where sterically hindered amines such as aliphatic diamines and amino alcohols have previously been used in gas sweetening to form carbonates or bicarbonates from carbon dioxide, or to form sulfides or bisulfides from hydrogen sulfide reactions, such processes have typically involved a regeneration step to recover the carbon dioxide or hydrogen sulfide. During the regeneration step, the carbon dioxide or hydrogen sulfide is liberated from the process fluid. A process and composition are therefore needed that will convert hydrogen sulfide to a stable, nontoxic and noncorrosive form without a corresponding need for regeneration of process fluids.
While the previously known hydrogen sulfide converters may theoretically require 1 to 2 ppm of converter per ppm of hydrogen sulfide in the treated fluid, amounts ranging from about 6 to 10 or more ppm of conventional converter per ppm of hydrogen sulfide are often required in actual practice because of difficulties encountered in distributing the converter evenly throughout the fluid.
Some conventional, commercially available products being marketed for use in hydrogen sulfide removal are unstable under storage and operating conditions, and can yield free formaldehyde. Products that can yield free formaldehyde are generally considered to be hazardous and environmentally unacceptable. A hydrogen sulfide and organic sulfide converter is therefore needed that is effective and economical, but less hazardous to the public and the environment.